The present invention generally relates to communication apparatuses, and more particularly to a communication apparatus which is provided with a driving mechanism and a speaker-phone.
Recently, various functions have been added to communication apparatus, and there is a communication apparatus which has a speaker-phone function (or hand-free function) which enables a call without unhooking a handset. Facsimile machines and multi-function telephone sets are examples of such a communication apparatus. The communication apparatus having the speaker-phone function is provided with a speaker for outputting the information which is received from the other end of the telephone line and a microphone for inputting the information which is to be transmitted to the destination via the telephone line.
On the other hand, the communication apparatus having the speaker-phone function is usually provided with a driving mechanism. In the case of a facsimile machine, for example, a scanner part has a document transport mechanism and a plotter part has a recording sheet transport mechanism. In the case of a multi-function telephone set, a cassette tape recorder is provided for use in an answering phone mode, for example.
But in the conventional communication apparatus having the speaker-phone function, the microphone is arranged at a position with an emphasis on picking up the sound and the speaker is arranged at a position with an emphasis on audibility. Hence, there is a problem in that the sound from the speaker is picked up by the microphone to generate what is so-called howling. In the communication apparatus which is provided with the driving mechanism, there are cases where the driving mechanism and the speaker-phone function are used simultaneously, owing to the various functions available on the communication apparatus. For example, the driving mechanism and the speaker-phone function are used simultaneously when recording the contents of the call made via the speaker-phone on the cassette tape recorder in the case of the telephone set provided with the cassette tape recorder, when recording a message on a first line in the answering phone mode while making a call on a second line via the speaker-phone in the case of the telephone set which accommodates two lines, and when making a facsimile communication on a first line while making a call on a second line via the speaker-phone in the case of the facsimile machine which accommodates two lines. In these cases, there is a problem in that the call is interfered with by noise which is generated by the driving sound of the driving mechanism picked up on the microphone of the speaker-phone.
In order to prevent the howling of the speaker-phone, it is conceivable to switch the transmission function and the reception function of the speaker-phone depending on a result of a comparison of the transmission signal level from the microphone and the reception signal level from the line. However, when the speaker-phone and the driving mechanism are used simultaneously, there is a problem in that the speaker-phone is constantly set to the transmission mode when the driving sound is generated and picked up on the microphone.
On the other hand, when the driving mechanism operates while the speaker-phone is in use, there is a problem in that it is difficult to understand the received message from the speaker due to the noise generated by the driving mechanism. To overcome this problem, a Japanese Laid-Open Patent Application No. 59-230356 proposes to detect a surrounding noise level and to control a gain compression circuit and a gain expansion circuit of the reception system based on the detected noise level. However, the communication apparatus becomes expensive in this case because of the need to detect the surrounding noise level. In addition, since the volume itself is constant, there is a problem in that it is still difficult to understand the received message from the speaker when the noise level increases due to the operation of the driving mechanism.